The invention relates to an oil filter for an internal combustion engine, especially for motor vehicles, comprising a filter housing, a filter cartridge that is exchangeably arranged in the interior of the filter housing, as well as a drainage valve arranged in the filter housing. The invention further relates to a filter cartridge for such an oil filter.
EP 1 674 142 A1 discloses an oil filter of an internal combustion engine wherein in the interior of its filter housing an exchangeable filter cartridge is arranged. Moreover, the filter housing is provided with a drainage valve at its lower end (relative to the direction of action of gravity), by means of which the filter housing can be drained when exchanging the filter cartridge. In a valve seat of the drainage valve there is a valve member that is movable coaxially to the longitudinal axis of the oil filter and that is locked to a terminal disk of the filter cartridge.
When servicing the oil filter the lower part of the filter housing is unscrewed and pulled downwardly while the filter cartridge initially remains in the operating position in the top part of the filter housing. When removing the lower part of the filter housing, the valve member that is locked to the filter cartridge is moved in the opening direction oriented toward the interior of the filter housing relative to the valve seat so that the drainage valve is opened. The oil that is contained in the interior of the filter housing drains through the open drainage valve in a controlled fashion. Subsequently, the filter cartridge is exchanged.
The assembly is done in reverse order: when axially pushing the bottom part of the filter housing onto the top part, the valve member locked to the filter cartridge is pushed into the valve seat in the closing direction opposite to the opening direction until it meets an axial stop.
Since the valve member when opening the filter housing is pulled out of the valve seat because of its fixed connection to the filter cartridge but remains attached to the filter cartridge, the user can remove the valve member from the used filter cartridge and insert it together with a new filter cartridge. However, this requires that the reusable valve member inclusive its sealing rings must be designed for a long service life by means of complex measures. Also, after multiple reuse of the valve member, there is no guarantee that no damage is done to the sealing rings and that a permanent seal tightness is maintained.
Moreover, the terminal disk of the filter cartridge in the area of the locking connection for the valve member is of solid material. In this way, an oil-tight separation of the interior of the filter cartridge from the exterior is provided. By means of the drainage valve of the filter housing the oil that is located at the unfiltered side of the filter cartridge can be drained but the residual oil in the interior, i.e., at the purified or filtered side, cannot be drained. When removing the used filter cartridge, special care must be taken that no used oil is spilled from the filter cartridge.